Purification, characterization, and immunomodulatory activity of a lectin from the seeds of horse chestnut (Aesculus hippocastanum L.)

Abstract

This work aimed to purify, characterize, and evaluate the immunomodulatory activity of a lectin from Aesculus hippocastanum seeds (AhSL). The lectin was isolated from saline extract through chromatography on a DEAE-Sephadex column. Protein homogeneity and subunit composition were evaluated with polyacrylamide gel electrophoresis (PAGE) under native and denaturing (SDS-PAGE) conditions, respectively. AhSL was evaluated for trypsin inhibitor activity, carbohydrate-binding specificity, and the effects of cations (Ca2+, Mn2+, and Mg2+), temperature, and pH on its hemagglutinating activity. Lectin stability under heating and pH variation was evaluated through fluorometric analysis. The activity of this lectin (12.5 µg/mL) in modulating cytokine release and nitric oxide production by mouse splenocytes was assessed. Isolated AhSL (purification fold: 68.8) showed a single polypeptide band in PAGE for acidic proteins and two polypeptide bands of approximately 68 and 124 kDa in SDS-PAGE. Its hemagglutinating activity was inhibited by monosaccharides, disaccharides, and glycoproteins, but was not affected by cations, and remained stable after heating (30–100 °C) and under pH 4.0–8.0. Fluorometric analysis revealed that the overall lectin conformation was not altered after heating to 100 °C and remained stable under various pH values. AhSL also showed trypsin inhibitor activity (specific activity: 1,280.31 U/mg) and induced the release of interleukins 10 and 6, tumor necrosis factor α, and nitric oxide by splenocytes. In conclusion, AhSL is a bioactive protein with promising biotechnological potential, which may find applications as immunological targeting or antitumor agents.

Keywords

• Multifunctional protein
• Cytokines
• Medicinal plant
• Thermostable protein